After a great deal of messing around and experimentation, I have resolved the problem.
On the other 7081 I have, the meter accepted the calibrate reference command with the
"reference supply of approximately 10 volts DC"
connected to the front panel input.
On this meter this reference supply needed to be applied to the "ratio reference" input DIN socket on the REAR panel. Once this was done all was well.
I completely fail to comprehend how this command actually worked on the other meter, as it is now clear that "calibrate reference" is actually doing the RATIO calibration.
So on page 8.11 of your maintenance manual you should amend the bullet point near the top of the page which reads:
* Connect a reference of approximately 10 volts dc to the input.
so that it reads:
* Connect a reference of approximately 10 volts dc to the ratio reference input on the rear of the meter.
Dave
-----Original Message-----
From: volt-nuts [mailto:volt-nuts-bounces at febo.com] On Behalf Of David C. Partridge
Sent: 21 April 2016 20:53
To: 'Discussion of precise voltage measurement'; Solartron_Schlumberger_Equipment at groups.io
Subject: [volt-nuts] Solartron 7081 calibration problems
> When I try to issue calibrate, reference, 10.00000 I get a message "Factor out of range" (all other VDC, VAC, and KOHM calibrate commands worked apart from the Cal Incomplete message).